U.S. DEPARTMENT OF THE INTERIOR
U.S. GEOLOGICAL  SURVEY 


Elevation Maps of the San Francisco Bay Region, California: A Digital Database


By SCOTT E. GRAHAM1 and RICHARD J. PIKE1



A portrayal of the most accurate data on the region's topography, 
35,000,000 digital elevations spaced 30 meters apart


OPEN-FILE REPORT 98-625

1998


This report is preliminary and has not been reviewed for conformity with U.S. Geological Survey editorial standards or 
with the North American Stratigraphic Code.  Any use of trade, product, or firm names is for descriptive purposes 
only and does not imply endorsement by the U.S. Government.

This database, identified as "Elevation Map of the San Francisco Bay Region, California: A Digital Database," has been 
approved for release and publication by the Director of the USGS.  Although this database has been subjected to 
rigorous review and is substantially complete, the USGS reserves the right to revise the data pursuant to further 
analysis and review.  Furthermore, it is released on condition that neither the USGS nor the United States Government 
may be held liable for any damages resulting from its authorized or unauthorized use.

1MENLO PARK, CA  94025




PREFACE

Topography, the configuration of the land surface, plays a major role in various natural processes 
that have helped shape the ten-county San Francisco Bay region and continue to affect its 
development.  Such processes include a dangerous type of landslide, the debris flow (Ellen and
others, 1997) as well as other modes of slope failure that damage property but rarely threaten life 
directly÷slumping, translational sliding, and earthflow (Wentworth and others, 1997).  Different 
types of topographic information at both local and regional scales are helpful in assessing the 
likelihood of slope failure and the mapping the extent of its past activity, as well as addressing 
other issues in hazard mitigation and land-use policy.  The most useful information is quantitative. 

INTRODUCTION TO THE DIGITAL DATABASE

This Open-File report is a digital map database.  This pamphlet serves to introduce and describe 
the digital data.  There are no paper maps included in the Open-File report.  The report does 
include, however, PostScript, and Portable Document Format (PDF) plot files containing images 
of the map sheets depicting elevation of the San Francisco Bay region and each of its ten 
constituent counties.

For those interested in the elevation maps, but who do not use an ARC/INFO compatible 
Geographic Information System (GIS), and would like to obtain the paper maps, 11 PostScript plot 
files and 11 PDF files containing map images of the data in the digital database have been 
included in the database package (please see the section "PostScript and PDF Plot Files Packages" 
page 9).  A PostScript plot file and PDF file showing problematic areas in the DEM from which 
the elevation database was derived are also included.  Note that the PostScript plot files require 
gzip and tar utilities to access the files.

For those without computer capability, we can provide users with the PostScript plot files or PDF 
files on tape that can be used by other vendors.  Additionally, plots can be ordered from the USGS 
via the plot-on-demand program once it has been initiated (please see the section "Obtaining Plots 
from USGS Open-File Services" page 9)
  
The content and character of the database, methods of obtaining it, and processes of extracting the 
map database from the tar file are described herein.  The map database itself, consisting of eleven 
ARC/INFO GRIDs and two ARC/INFO coverages, can be obtained over the Internet or by 
magnetic tape copy as described below. 

The database was compiled using ARC/INFO, a commercial Geographic Information System 
(Environmental Systems Research Institute, Redlands, California), with version 3.0 of the menu 
interface ALACARTE (Fitzgibbon and Wentworth, 1991, Fitzgibbon, 1991, Wentworth and 
Fitzgibbon, 1991).  The ARC/INFO GRIDs are stored in compressed tar files, and the coverages 
are stored in uncompressed ARC export format (ARC/INFO version 7.x) in a compressed UNIX 
tar (tape archive) file. All data files have been compressed, and may be uncompressed with gzip, 
which is available free of charge over the Internet via links from the USGS Public Domain 
Software page (http://edcwww.cr.usgs.gov/doc/edchome/ndcdb/public.html).  A tar utility is 
required to extract the databases from tar files.  This utility is included in most UNIX systems,  
and can be  obtained free of  charge  via  the  Internet  from   Internet Literacy's Common Internet 
File Formats Webpage (http://www.matisse.net/files/formats.html) for Macintosh and Windows.  
If you are using a Windows machine, WinZip is also capable of dealing with both gzip 
compression and tar files.  ARC/INFO export files (files with the .e00 extension) can be converted 
into ARC/INFO coverages in ARC/INFO (see below) and can be read by some other Geographic 
Information Systems, such as MapInfo via ArcLink and ESRI's ArcView.


THE DIGITAL ELEVATION-MAP DATABASE

The data from which the new maps were computed consist of a digital elevation model (DEM), an 
(X,Y) array of terrain heights spaced 30 m apart.  We assembled the data set from 204 separate 
DEM's derived from topographic maps in the USGS 7.5' series (see the quadrangle index map, 
Figure 1 in Pike, 1997).  Because all constituent DEM's were created by the recent and higher-
accuracy "Level II" procedures that interpret elevations from digital line graphs of the map 
contours (U.S. Geological Survey, 1993), these maps are free from the striped artifacts that mar 
shaded-relief portrayals computed from older 7.5' DEM's.  A few problems in the DEM remain, 
principally minor edgematch errors, and are identified in a separate map.

At 1:275,000 scale, the full Bay Region map comprises some 35,000,000 rectangular picture 
elements (pixels), each about 0.11 mm across.  The array measures 7743 cells in the east-west 
direction and 7423 cells in the north-south direction.  Pixels of the ten 1:125,000-scale county 
maps, at about 0.24 mm across, are below the size at which the human eye begins to resolve 
individual elements.

Drainage lines and nearshore bathymetry, and major roads from an existing digital base (Aitken, 
1997) were added to elevation on all 11 maps.  A two-km buffer zone around all counties was 
added to each 1:125,000-scale map to provide context for any terrain details at or near the county 
boundary (mapped by a white-bounded black line).

The database for the elevation map consists of ARC/INFO GRIDs for the region as a whole and 
for each of the ten counties, an ARC/INFO vector coverage identifying areas of the DEM 
compilation that have edgematch or other problems, PostScript map-image files for each of those 
11 areas, a PostScript version of a map showing the problematic areas, and a PostScript version of 
this text.  Additionally, a PDF file for each of the PostScript plot files has been included. 

The 204 7.5 minute DEM's were compiled into a single dataset using the LATTICEMERGE 
command in ARC/INFO.  Most of the inconsistencies and edgematch problems between adjacent 
quadrangles were cleaned up using the FOCALMEAN function in ARC/INFO GRID.  A number 
of these problems still exist (see of98-625_5l.ps or of98-625_5l.pdf). 






We selected 12 elevation ranges, designated  in the plotfiles by different colors, to enhance 
presentation of the new data.  Slope intervals and their associated colors are:

0-25 meters
25-50 meters
50-100 meters
100-200 meters
200-300 meters
300-400 meters
400-500 meters
500-600 meters
600-800 meters
800-1000 meters
1000-1200 meters
>1200 meters

The map database itself is rather simple, consisting of attributed GRID cells stored in Universal 
Transverse Mercator (UTM) projection (Table 1). 


Table 1 - Map Projection

PROJECTION		UTM
ZONE			10
DATUM			NAD27
ZUNITS			decimeters
UNITS			meters
PARAMETERS		none


Content of the map database can be described in terms of the grid cells comprising the map.  
Descriptions of the database fields use the terms explained in Table 2.


Table 2 - Field Definition Terms

ITEM NAME		name of the database field (item)
WIDTH			maximum number of digits or characters stored
OUTPUT			output width
TYPE			B-binary integer, F-binary floating-point number,
			I-ASCII integer, C-ASCII character string
N.DEC			number of decimal places maintained for floating-
			point numbers


The database format of the grid is described in tables 3 and 4, which show the format of the GRID 
attribute and statistics tables.


Table 3 - Contents of GRID Value Attribute Table (<GRIDNAME>.VAT)

	ITEM NAME	     WIDTH    OUTPUT	TYPE	N.DEC

     	AREA	      		4	10	  B	  --
     	COUNT	      		4	10	  B	  --


Table 4 - Contents of GRID Statistics Table (<GRIDNAME>.STA)

        ITEM NAME	WIDTH	OUTPUT	TYPE	N.DEC
	MIN              8	  15     F        3
        MAX              8	  15     F        3
        MEAN             8	  15     F        3
        STDV             8	  15     F        3


LINES

The lines (arcs) are recorded as strings of vectors and are described in the arc attribute table 
(tables 5 and 7).  They define the boundaries of the map units, the boundaries of open bodies of 
water, and the map boundaries.  These distinctions, including the geologic identities of the 
unit boundaries, are recorded in the LTYPE field according to the line types listed in tables 
6 and 8.

Table 5 - Contents of the Arc Attribute Table  (DEMPROBS.AAT)

ITEM NAME     WIDTH   OUTPUT  TYPE  N. DEC	

FNODE#		4	5	B		starting node of arc (from node)   
TNODE#		4	5	B		ending node of arc (to node)
LPOLY#		4	5	B		polygon to the left of the arc
RPOLY#		4	5	B		polygon to the right of the arc
LENGTH		4	12	F	3	length of arc in meters 
<coverage>#	4	5	B		unique internal control number
<coverage>-ID	4	5	B		unique identification number
LTYPE		35	35	C		line type (see Tables 4 and 5) 
SEL		1	1	I		user defined field used to save a 
                                                  selected set
SYMB		3	3	I		user defined field used to save
                                                  symbol assignments (such as color)





Table 6 - Line Types Recorded in the LTYPE Field  (DEMPROBS.AAT)

problem


Table 7 - Contents of the Arc Attribute Table  (SFBR-QI.AAT)

ITEM NAME     WIDTH   OUTPUT  TYPE  N. DEC	

FNODE#		4	5	B		starting node of arc (from node)   
TNODE#		4	5	B		ending node of arc (to node)
LPOLY#		4	5	B		polygon to the left of the arc
RPOLY#		4	5	B		polygon to the right of the arc
LENGTH		4	12	F	3	length of arc in meters 
<coverage>#	4	5	B		unique internal control number
<coverage>-ID	4	5	B		unique identification number
LTYPE		35	35	C		line type (see Tables 4 and 5) 
SEL		1	1	I		user defined field used to save a 
                                                   selected set
SYMB		3	3	I		user defined field used to save
 	                                           symbol assignments (such as color)
TICS		4	4	C


Table 8 - Line Types Recorded in the LTYPE Field  (SFBR-QI.AAT)

15
7.5
santa cruz


AREAS

Map units (polygons) are described in the polygon attribute table (tables 8 and 10).  The identities 
of  the map units are shown in tables 9 and 11. 



Table 8 - Content of the Polygon Attribute Tables  (DEMPROBS.PAT)

ITEM NAME     WIDTH   OUTPUT  TYPE  N. DEC	
	
AREA		4	12	F	3	area of polygon in square meters
PERIMETER	4	12	F	3	length of perimeter in meters
<coverage>#	4	5	B		unique internal control number
<coverage>-ID	4	5	B		unique identification number 
PTYPE		35	35	C		unit label (see Tables 7 and 8)
SEL		1	1	I		user defined field used to save 
						   a selected set
SYMB		3	3	I		user defined field used to save 
					           symbol assignments (such as color)


Table 9 - Polygon types recorded in the PTYPE field  (DEMPROBS.PAT)

problem


Table 10 - Content of the Polygon Attribute Tables  (SFBR-QI.PAT)

ITEM NAME     WIDTH   OUTPUT  TYPE  N. DEC	
	
AREA		4	12	F	3	area of polygon in square meters
PERIMETER	4	12	F	3	length of perimeter in meters
<coverage>#	4	5	B		unique internal control number
<coverage>-ID	4	5	B		unique identification number 
NAME            35      35      C               7.5 minute quadrangle name


Table 11 - Polygon types recorded in the NAME field (SFBR-QI.PAT)


 AETNA SPRINGS
 ALLENDALE
 ALTAMONT
 ANNAPOLIS
 ANO NUEVO
 ANTIOCH NORTH
 ANTIOCH SOUTH
 ARCHED ROCK
 ASTI
 BENICIA
 BIG BASIN
 BIG FOOT MTN
 BIRD VALLEY
 BIRDS LANDING
 BODEGA HEAD
 BOLINAS
 BOULDIN ISLAND
 BRENTWOOD
 BRIONES VALLEY
 BROOKS
 BYRON HOT SPRINGS
 CALAVERAS RESERVOIR
 CALISTOGA
 CAMP MEEKER
 CAPELL VALLEY
 CASTLE ROCK RIDGE
 CAZADERO
 CEDAR MTN
 CHILES VALLEY
 CHITTENDEN
 CLARKSBURG
 CLAYTON
 CLIFTON COURT FOREBAY
 CLOVERDALE
 COPPER MOUNTAIN
 CORDELIA
 COTATI
 COURTLAND
 CREVISON PEAK
 CUPERTINO
 CUTTINGS WHARF
 DAVENPORT
 DAVIS
 DENVERTON
 DETERT RESERVOIR
 DIABLO
 DIXON
 DOUBLE POINT
 DOZIER
 DRAKES BAY
 DUBLIN
 DUNCAN MILLS
 ELDORADO BEND
 ELMIRA
 ESPARTO
 EYLAR MTN
 FAIRFIELD NORTH
 FAIRFIELD SOUTH
 FELTON
 FORT ROSS
 FRANKLIN POINT
 GEYSERVILLE
 GILROY
 GILROY HOT SPRINGS
 GLEN ELLEN
 GRAYS BEND
 GUALALA
 GUDE MOUNTAIN
 GUERNEVILLE
 GUINDA
 HALF MOON BAY
 HAYWARD
 HEALDSBURG
 HONKER BAY
 HUNTERS POINT
 INVERNESS
 ISABEL VALLEY
 ISLETON
 JERICHO VALLEY
 JERSEY ISLAND
 JIMTOWN
 KENWOOD
 KNIGHTS LANDING
 KNOXVILLE
 LA COSTA VALLEY
 LA HONDA
 LAKE BERRYESSA
 LAS TRAMPAS RIDGE
 LATHROP
 LAUREL
 LIBERTY ISLAND
 LICK OBSERVATORY
 LIVERMORE
 LOMA PRIETA
 LONE TREE CREEK
 LOS GATOS
 MADISON
 MANTECA
 MARE ISLAND
 MARIPOSA PEAK
 MARK WEST SPRINGS
 MCGUIRE RIDGE
 MENDENHALL SPRINGS
 MERRITT
 MIDDLETOWN
 MIDWAY
 MILPITAS
 MINDEGO HILL
 MISSISSIPPI CREEK
 MONTARA MTN
 MONTICELLO DAM
 MORGAN HILL
 MOUNT ST HELENA
 MOUNTAIN VIEW
 MT BOARDMAN
 MT DAY
 MT GEORGE
 MT MADONNA
 MT SIZER
 MT STAKES
 MT VACA
 MUSTANG PEAK
 NAPA
 NEWARK
 NILES
 NOVATO
 OAKLAND EAST
 OAKLAND WEST
 ORESTIMBA PK
 PACHECO PASS
 PACHECO PEAK
 PALO ALTO
 PATTERSON
 PETALUMA
 PETALUMA POINT
 PETALUMA RIVER
 PIGEON POINT
 PLANTATION
 POINT BONITA
 POINT REYES NE
 REDWOOD POINT
 RICHMOND
 RIO VISTA
 RIPON
 RUTHERFORD
 SACRAMENTO WEST
 SAN FELIPE
 SAN FRANCISCO NORTH
 SAN FRANCISCO SOUTH
 SAN GERONIMO
 SAN GREGORIO
 SAN JOSE EAST
 SAN JOSE WEST
 SAN LEANDRO
 SAN MATEO
 SAN QUENTIN
 SAN RAFAEL
 SANTA CRUZ
 SANTA ROSA
 SANTA TERESA HILLS
 SAUNDERS REEF
 SAXON
 SEARS POINT
 SEBASTOPOL
 SOLYO
 SONOMA
 SOQUEL
 ST HELENA
 STEWARTS POINT
 TASSAJARA
 TAYLOR MONUMENT
 THE GEYSERS
 THREE SISTERS
 TOMALES
 TOMBS CREEK
 TRACY
 TWO ROCK
 UNION ISLAND
 VALLEY FORD
 VERNALIS
 VERONA
 VINE HILL
 WALNUT CREEK
 WALTER SPRINGS
 WARM SPRINGS DAM
 WATSONVILLE EAST
 WATSONVILLE WEST
 WESTLEY
 WHISPERING PINES
 WILCOX RIDGE
 WINTERS
 WOODLAND
 WOODSIDE
 WOODWARD ISLAND
 YOUNTVILLE
 ZAMOR



DATABASE CONTENTS

The digital map database consists of digital files representing the five parts of the database, some 
of which are presented in more than one format.  The names of the files are unique designators 
based on the report identifier, of98-625, followed by part numbers and an extension indicating file 
type.  The larger files, which have been compressed with gzip, have .gz extensions as well.  

1. Revision List
A list of the parts of the report and at what version number of the report each was last revised (if at 
all) followed by a chronologic list that describes any revisions.
	a. of98-625revs_1a.txt		ASCII file


2. Open File Text
The text of the open-file report (this document), which describes the database and how to obtain it.
	a. of98-625_2a.txt			unformatted ASCII text
	b. of98-625_2b.ps			PostScript file
      	c. of98-625_2c.pdf			PDF file


3.  Elevation Database
A separate GRID (ARC/INFO raster digital map database) is included for each of the ten counties 
in the San Francisco Bay region, as well as one for the Bay region as a whole.  The GRIDs, which 
have been packaged in tar (tape archive) files, are described below.

----------------------------------------------------------------------------------------------------
ARC/INFO	      	Size of gzip	Resultant	Description of
export file	      	compressed	Grid,		Grid or Coverage	       	
or tar file	  	tar file	Coverage	
		      	(uncompressed)	or file(s)
-----------------------------------------------------------------------------------------------------
of98-625_3a.tar     	30 MB (49 MB) 	sfbr-el         SF Bay region elevation GRID
of98-625_3b.tar       	2.5 MB (4.3 MB) al-el 		Alameda County elevation GRID
of98-625_3c.tar       	2.2 MB (4.1 MB) cc-el 		Contra Costa County elevation GRID
of98-625_3d.tar         2 MB (3.6 MB) 	ma-el 		Marin County elevation GRID
of98-625_3e.tar        	3.3 MB (5.5 MB)	na-el 		Napa County elevation GRID
of98-625_3f.tar         224 KB (496 KB) sf-el 		San Francisco County elevation GRID
of98-625_3g.tar         2 MB (3.2 MB) 	sm-el 		San Mateo County elevation GRID
of98-625_3h.tar        	6 MB (8.9 MB)	scl-el 		Santa Clara County elevation GRID
of98-625_3i.tar      	2.3 MB (3.6 MB) scr-el 		Santa Cruz County elevation GRID
of98-625_3j.tar    	1.9 MB (3.5 MB) sol-el 		Solano County elevation GRID
of98-625_3k.tar      	5.5 MB (9.9 MB) son-el 		Sonoma County elevation GRID

4. Quadrangle Index and DEM Problems databases
The data files representing the lines and polygons of the quadrangle index and problems associated 
with the SF Bay region DEM from which the slope map was derived (ARC export and ARCVIEW 
shape formats).

-------------------------------------------------------------------------------------------
ARC/INFO	      	Size of gzip	 Resultant	Description of
export file	      	compressed	 Grid,		Grid or Coverage	       	
or tar file	  	tar file	 Coverage	
		      	(uncompressed)	 or file(s)
-------------------------------------------------------------------------------------------
of98-625_4a.e00		256 KB (1.1 MB)	 sfbr-qi   	SF Bay region Quadrangle Index 
							(ARC/INFO export file)

of98-625_4b.tar		272 KB (912 KB)	 sfbrqiln	SF Bay region Quadrangle Index
					 sfbrqipy	(ARCVIEW shape files)

of98-625_4c.e00 	7 KB (27 KB)	 demprobs  	DEM problem areas (ARC/INFO export file)

of98-625_4d.tar		4 KB (22 KB)	 probsln	DEM problem areas (ARCVIEW shape files)
					 probspy	

For the map identifying problematic areas in the source DEM, and the accompanying quadrangle 
index map, only a coverage for the entire SF Bay region is included.  There are no separate county 
databases.  The coverages, along with their associated INFO directory have been converted to 
uncompressed ARC/INFO export files.  ARC export files promote ease of data handling, and are 
usable by some Geographic Information Systems in addition to ARC/INFO (see below for a 
discussion of working with export files).  The ARCVIEW shapefile packages each consist of three 
files - <name>.dbf, <name>.shp, and <name>.shx.



5. PostScript and PDF plot files
Slope maps of the SF Bay Region and each of its ten constituent counties in PostScript and PDF 
formats.  Note, the PDF files have not been compressed.  The file sizes listed for them below are
the actual sizes of the PDF files.

--------------------------------------------------------------------------------------
Plot file		Size of gzip	
			compressed		Description of plot file
			plot file	
			(uncompressed)  
--------------------------------------------------------------------------------------
of98-625_5a.ps     	16.8 MB (371.4 MB)	SF Bay region elevation map (PostScript)
of98-625_5b. ps		3.9 MB (46.1  MB)	Alameda County elevation map (PostScript)
of98-625_5c. ps		3.6 MB (42.1 MB)	Contra Costa County elevation map (PostScript)
of98-625_5d.ps      	3 MB (36.7 MB)    	Marin County elevation map (PostScript)
of98-625_5e.ps      	3.8 MB (43 MB)    	Napa County elevation map (PostScript)
of98-625_5f.ps		976 KB (9.1 MB)  	San Francisco County elevation map (PostScript)
of98-625_5g.ps     	2.5 MB (31 MB)  	San Mateo County elevation map (PostScript)
of98-625_5h.ps      	5.3 MB (66 MB) 		Santa Clara County elevation map (PostScript)
of98-625_5i.ps		3 MB (37.2 MB) 		Santa Cruz County elevation map (PostScript)
of98-625_5j.ps     	3.5 MB (45.5 MB)    	Solano County elevation map (PostScript)
of98-625_5k.ps     	5.8 MB (82 MB)		Sonoma County elevation map (PostScript)
of98-625_5l.ps		5.8 MB (21 MB)		Map of problems associated with SF
						Bay region DEM (PostScript)

of98-625_5a.pdf   	7.6 MB	   		SF Bay region elevation map (PDF)
of98-625_5b.pdf		2.7 MB 			Alameda County elevation map (PDF)
of98-625_5c.pdf		2.7 MB 			Contra Costa County elevation map (PDF)
of98-625_5d.pdf		2 MB			Marin County slope elevation (PDF)
of98-625_5e.pdf		2.4 MB			Napa County slope elevation (PDF)
of98-625_5f.pdf		792 KB			San Francisco County elevation map (PDF)
of98-625_5g.pdf		1.7 MB			San Mateo County elevation map (PDF)
of98-625_5h.pdf		3.3 MB 	   		Santa Clara County elevation map (PDF)
of98-625_5i.pdf		1.8 MB 			Santa Cruz County elevation map (PDF)
of98-625_5j.pdf		2.6 MB 			Solano County elevation map (PDF)
of98-625_5k.pdf		3.3 MB 	  		Sonoma County elevation map (PDF)
of98-625_5l.pdf		5.7 MB			Map of problems associated with SF
						Bay region DEM (PDF)


OBTAINING PLOTS FROM USGS OPEN-FILE SERVICES

NOTE:  As of this writing, plot-on-demand is not available from USGS.  This service may not 
begin until 1999.

U.S. Geological Survey is planning to provide a plot-on-demand service for map files, such as 
those described in this report, through Open-File Services.  In order to obtain plots, contact Open-
File Services at:

USGS Information Services
Box 25286
Denver Federal Center
Denver, CO 80225-0046

(303) 202-4200
1-800-USA-MAPS

FAX:  (303) 202-4695

e-mail:  infoservices@usgs.gov

Be sure to include with your request the Open-File Report number and the exact names, as listed 
in the Database Contents section above, of the plot file(s) you require.  An Open-File Report 
number and its letter alone are not sufficient, unless you are requesting plots of all the plot files for 
this report (as many as 12 plot files!).


POSTSCRIPT PLOT FILE PACKAGE

For those interested in the any of the elevation maps of the SF Bay region who don't use an 
ARC/INFO compatible GIS system, but would like to obtain any of the paper maps, we have 
included separate PostScript and PDF plot files for each of the ten counties and the Bay Region, as 
well as for the map delineating problem areas in the composite DEM for the SF Bay region.  

The plot files are available in any of the three ways described below, including the World Wide Web 
pages.  The plot files have been compressed with gzip and they must be uncompressed to access 
them.   The compression utility gzip is available free of charge for Windows, Macintosh and Unix 
platforms via the Internet from the gzip home page (http://w3.teaser.fr/~jlgailly/gzip).  

The PostScript images are as large as 36 inches wide by 40 inches high, so they require a large 
plotter to produce paper copies at the intended scale.  Because this release is primarily a digital 
database, the plot files (and plots derived therefrom) hve not been edited to conform to U.S. 
Geological Survey standards.  



OBTAINING THE POSTSCRIPT OR PDF PLOT FILES

The PostScript and PDF plot files can be obtained in any of three ways:

1.  Sending a tape with request
A compressed plot file(s) can be obtained by sending a tape with request to: 

 	SFBR Elevation Map Plot File
	c/o Database Coordinator
	U.S. Geological Survey
	345 Middlefield Road, MS 975
	Menlo Park, CA 94025

The compressed tar file will be returned on the tape.  The acceptable tape types are:

2.3 or 5.0 GB, 8 mm Exabyte tape.

Be sure to include with your request the Open-File Report number and the exact names, as listed 
in the Database Contents section above, of the plot file(s) you require.  An Open-File Report 
number and its letter alone are not sufficient, unless you are requesting plots of all the plot files for 
that report (as many as 12 plot files!).

2.  Anonymous ftp over the Internet

To obtain plotfiles by ftp:

The files in these reports are stored on the U.S. Geological Survey Western Region FTP server.  
The Internet ftp address of this server is:

	ftp://wrgis.wr.usgs.gov

The user should log in with the user name Îanonymousâ and then input their e-mail address as the 
password.  This will give the user access to all the publications available via ftp from this server.

The files in this report are stored in the subdirectory:

	pub/open-file/of98-625

3.  From the Western Region Geologic Information Web Page.

The U.S. Geological Survey now supports a set of graphical pages on the World Wide Web.  
Digital publications (including this one) can be accessed via these pages.  The web server for 
digital publications from the Western Region is "http://wrgis.wr.usgs.gov".  Once at the main 
page, click on 'Geologic Map Databases' under the heading 'Data Online'; next click on 
'California.'  Scroll down to the section for this database and click on the Open-File button to get 
to this publication's web page.  Click on 'Open-File Report 98-625'; this will take you to the web 
page for this database.  Set your web browser to save to a local disk and click on the link for the 
desired file to download the compressed PostScript plot file or PDF file.

For those interested in the elevation map of the bay region, any of its ten constituent counties, or 
the map showing problems with the SF Bay region DEM who do not use computers, we will also 
provide any of the PostScript or PDF plot files on digital tape for use by other vendors.  The 
PostScript or PDF plot files can be obtained by sending a tape with request and return address to:

	SFBR Elevation Map Plot File
	c/o Database Coordinator
	U.S. Geological Survey
	345 Middlefield Road, MS 975
	Menlo Park, CA 94025

The compressed plot file(s) will be returned on the tape.  The acceptable tape types are:

	2.3 or 5.0 GB, 8 mm Exabyte tape.

Be sure to include with your request the Open-File Report number and the exact names, as listed 
in the Database Contents section above, of the plot file(s) you require.  An Open-File Report 
number and its letter alone are not sufficient, unless you are requesting plots of all the plot files for 
this report (as many as 12 plot files!).

Make sure your vendor is capable of reading these tape types and this PostScript plot file.  
Important information regarding tape file format is included in the section "PostScript Plot Files" 
below, so be certain to provide a copy of this document to your vendor.

	
 OBTAINING DIGITAL DATABASES

The digital database package can be obtained in any of three ways:

1.  Sending a tape with request
	
A compressed tar file(s) of the elevation map database for the bay region, any of its ten counties, 
or the DEM problems coverage can be obtained by sending a tape with request and return address 
to:

		SFBR Elevation Map Database
		c/o Database Coordinator
		U.S. Geological Survey
		345 Middlefield Road, M/S 975
		Menlo Park, CA 94025

The compressed tar file(s) will be returned on the tape.  The acceptable tape types are:

	2.3 or 5.0 GB, 8mm Exabyte tape.

Be sure to include with your request the Open-File Report number and the exact names, as listed 
in the Database Contents section above, of the database file(s) you require.  An Open-File Report 
number and its letter alone are not sufficient, unless you are requesting all of the database files for 
this report (as many as 15).

2.  Anonymous ftp over the Internet

To obtain digital database package by ftp:

The files in these reports are stored on the U.S. Geological Survey Western Region FTP server.  
The Internet ftp address of this server is:

	ftp://wrgis.wr.usgs.gov

The user should log in with the user name Îanonymousâ and then input their e-mail address as the 
password.  This will give the user access to all the publications available via ftp from this server.

The files in this report are stored in the subdirectory:

pub/open-file/of98-625

3.  From the Western Region Geologic Information Web Page.

To obtain the tar file via the World Wide Web:

The U.S. Geological Survey now supports a set of graphical pages on the World Wide Web. 
Digital geologic publications (including this one) can be accessed via these pages.  The web page 
for digital geologic publications from the Western Region (including this one) is  
ăhttp://wrgis.wr.usgs.govä.  Once at the main page, click on 'Geologic Map Databases' under the 
heading 'Data Online'; next click on 'California.'  Scroll down  to get to the listing for this 
database.  Click on 'Open-File Report 98-625'; this will take you to the web page for this 
database.  Set your web browser to save to a local disk and click on the link for the desired 
database to download the compressed tar file or ARC/INFO export file.

				
CONVERTING ARC EXPORT FILES

ARC export files are converted to ARC coverages using the ARC command IMPORT with the 
option COVER.   Change directories to the database directory.  From the ARC command line 
type:

Arc:  import cover <filename>.e00 <output coverage>

ARC export files can also be read by some other Geographic Information Systems.  Please consult 
your GIS documentation to see if you can use ARC export files and the procedure to import them.


ACKNOWLEGEMENTS

Thanks to Brian Bennett, Robert Lugo, and Douglas Aitken of National Mapping Division for 
providing assistance with obtaining the highest quality digital elevation models for use in this 
compilation.


REFERENCES CITED

Aitken, D.S., 1997, Digital version of the 1970 Topographic Map of the San Francisco Bay 
	Region: U.S. Geological Survey Open-file Report 97-500, three sheets, map scale 1:125,000.

Ellen, S.D., Mark, R.K., Wieczorek, G.F., Wentworth, C.M., Ramsey, D.W., and May, T.E.,
	1997, Map Showing Principal debris-flow source areas in the San Francisco Bay Region,
	California: U.S. Geological Survey, Open-file Report 97-745 E, map scales 1:275,000 and 1:125,000.

Fitzgibbon, T.T., 1991, ALACARTE installation and system manual (version 1.0): U.S. 
	Geological Survey, Open-File Report 91-587B.

Fitzgibbon, T.T., and Wentworth, C.M., 1991, ALACARTE user interface - AML code 
	and demonstration maps (version 1.0):  U.S. Geological Survey, Open-File Report 
	91- 587A.

Pike, R.J., 1997, Index to detailed maps of landslides in the San Francisco Bay
	Region,California: U.S. Geological Survey, Open-file Report 97-745 D.
	U.S. Geological Survey, 1970, Topographic map of the San Francisco Bay region: 3 sheets, scale 
	1:125,000.

U.S. Geological Survey, 1993, Digital elevation models, data users guide 5 (3rd printing, revised), 
	Reston, VA, National Mapping Program, Technical Instructions, 48 p.  [replaces 1987 ed. 
	(38 p.) & 1990 ed. (51 p.)]

Wentworth, C. M., and Fitzgibbon, T. T., 1991, ALACARTE user manual (version 1.0):  U. S.
	Geological Survey Open-File Report 91-587C.

Wentworth, C. M., Graham, S.E., Pike, R.J., Beukelman, G.S., Ramsey, D.W., and Barron, A.D., 
	1997, Summary distribution of slides and earth flows in the San Francisco Bay Region,
    	California: U.S. Geological Survey, Open-file Report 97-745 C, map scales 1:275,000 and
    	1:125,000.